In order to investigate fundamental characteristics of three-dimensional corner separations of decelerating cascade flow, a channel flow around a NACA65 blade in a decelerating flow by turning was examined. Two-dimensional calculations show that the NACA65 cascade flow that has 45deg. of turning, 1.24 of solidity and 17deg. of stagger angle is equivalent to the channel flow that has 14deg. of stagger angle in terms of pitchwise blade force. Experimental and numerical investigations show that the pitchwise periodicity of the wake at downstream of the blade is comparably good. Therefore, this channel flow is suitable for investigating the three-dimensional corner separations of decelerating cascade flow.